The passage of electrons through a barrier that, according to the principles of classical mechanics, cannot be breached. An example of electron tunneling is the passage of an electron through a thin insulating barrier between two superconductors. Electron tunneling is a pure quantum mechanical effect that cannot be explained by a classical theory.

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The passage of electrons through a barrier that, according to the principles of classical mechanics, cannot be breached. An example of electron tunneling is the passage of an electron through a thin insulating barrier between two superconductors. Electron tunneling is a pure quantum mechanical effect that cannot be explained by a classical theory.

Source